Roof-LinkConnecting a voltage sensor from the solar panel on the 12th floor of the Tisch building to an Xport on the 4th floor. This is done using an Xbee radio mesh network, with three Xbee radio modules: on the 12th floor, the 8th and the 4th. XBee Mesh Network:
12/FXbee powered by the solar panel (using a 3.3V regulator). Using an analog input pin, we connect the leads from the solar panel, through a series of resistors, to the analog pin (when doing analog readings its important to remember to connect the Vref pin of the Xbee chip to the maximum voltage in the circuit =>3.3V in this case). The Xbee takes the readings every once in a while and sends them down to the 8th floor xbee module. 12/f Xbee settings:
8/FXbee configuration here is the most difficult. We placed a little box that has just an Xbee radio with a 9V battery, on top of an electric box in the stairway. In order to conserve battery power, we activated sleep mode on the Xbee chip. The Rx pin is connected directly to the Tx pin here. So this Xbee radio wakes up every 15 seconds on average, checks for any messages from the 12th floor sensor, sends the message on down to the 4th floor module, and goes back to sleep. This saves a large amount of battery life. When sleeping, the Xbee consumes only 0.17mA (compared to 10mA) => this is without any LED's in the circuit... which also increase the amperage intake by 6. 8/f Xbee settings:
We've been testing out different batteries and how long they last for the 8/F module. Using a Duracell 9V battery, the 8/f module lasted only a couple of hours when not set to cyclic sleep. With it waking up every 8 seconds, it lasted around 1 week. Now we're trying to see how long the juice will last off a single Energizer 9V battery, when sleeping for a minute every time. This trial began on february 17th, evening. Didn't even last one week. Not sure why. Current trial, starting March 2nd, will attempt to use 4 rechargeable AA batteries, and keep the time before sleep (ST) minimal. 4/FXbee radio connected directly to an Xport. Now its possible to hit the Xport's IP directly from any script and get readings coming down this network during the day. Xbee settings:
|